Abstract
Ensuring the physical integrity of engineered barriers for an extremely long time period is necessary for geological disposal of high-level radioactive wastes.
This report describes the design process and the designed configurations of both overpack and buffer as engineered barriers. Manufacturing procedure, quality control and inspection methods are also summarized.
Carbon steel was selected as a structural material of the overpack and the specification of the overpack was determined assuming disposal in the depths of 1000m below surface of crystalline rock site.
The mixture of bentonite and sand (80% sodium bentonite and 20% silica sand by mass) was selected as material for a buffer from mainly its permeability and characteristics of self-sealing of a gap occurred in construction work.
Welding method of a lid onto the main body of the overpack, uniting method of a corrosion-resistance layer and the structural component in the case of a composite overpack and manufacturing procedures of both blocks-type and monolithic-type buffers are also investigated.
